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Most of the following insights are taken from 100 Things Every Designer Needs to Know About People by Susan M. Weinschenk. This is a living note that I will update with my latest UX learnings.
How people see
Peripheral vision v. central vision
Peripheral vision is used more than central vision to get the gist of what you see.
The theory is that early humans who were sharpening their flint or looking up at the clouds and yet still noticed that a lion was coming at them in their peripheral vision survived to pass on their genes.
The amygdala responds twice as fast to an emotional element in our peripheral vision than if it were in our central vision.
If you have images of an emotional nature, put them in the periphery instead of in the middle.
People are attracted to faces
There's a special part of the brain just for recognizing faces. People recognize and react to faces quickly, so if you want to grab attention, show faces.
Faces that are looking straight out at the viewer will have the greatest emotional impact, probably because the eyes are the most important part of the face.
We look where the faces look. This doesn't necessarily mean that they will pay attention to it or take action. It just means that they will look at it.
Differentiate one feature at a time
Having one element look different from any others is the best way to grab visual attention. Have one item be a different color / shape / orientation.
A mistake that designers sometimes make is to use several of these visual features together. If on one page or in one image you have several different colors, shapes, and angles, it may take the visual cortex longer to process that information. You won't be as effective in grabbing visual attention.
People see cues and act on them
A pair of scissors invites you to put fingers through the circles and move your thumb up and down to open and close. If the item gives you cues that don't work, you get annoyed and frustrated. These cues are called affordances.
When you're designing an application or website, think about the affordances of objects on the screen. For example, have you ever wondered what makes people want to click a button? Cues in the button's shadow tell people that it can be pushed in, the way a button on an actual device can be pushed in.
Avoid providing incorrect affordance cues. For instance, underlining a bit of text that is not a hyperlink.More info about UI affordances
People scan screens based on past experience and expectations
People tend to look for meaningful information about 30 percent in from the edge and 30 percent in from the top. They don't start scanning a page in the topmost corner because they have gotten used to the idea that there are things on screens and pages that are less relevant to the task at hand, such as logos and blank space.
Avoid putting task-related information at the edges, since people tend not to look there with central vision.
Save the edges for peripheral vision, which may include images with emotion or anything that will give the “gist” of the scene—for example, logos, branding, and navigation menus.
How we perceive colors
When lines or text of different colors are projected or printed, the depths of the lines may appear to be different. One color may jump out while another color appears recessed. This effect is called chromostereopsis. These color combinations can be hard and tiring to look at or read.
All in all, avoid putting blue and red or green and red near each other on a page or screen.
Nine percent of men and one‑half percent of women are color-blind. So the rule of thumb is that wherever you use color to give specific meaning, you need a redundant coding scheme—for example, color and line thickness—so that people who are color-blind will be able to decipher the code without needing to see specific colors.
Titles and typography for better comprehension
Reading and comprehending are two different things. If you want to make sure your content is easy to comprehend, here are a few things to keep in mind.
Providing meaningful titles and headlines are critical. It gives context to the following paragraphs and greatly improves comprehension of a text.
Choose your font wisely. If people have trouble reading the font, they will transfer that feeling of difficulty to the meaning of the text itself and decide that the subject of the text is hard to do or understand.
Based on a 2004 study:
- Use a longer line length (80 to 100 characters per line) if your reader needs to read quickly.
- Use a shorter line length (45 to 72 characters per line) if your reader doesn't necessarily need to read quickly.
How people remember
Short-term memory is very limited
Don't ask people to remember information from one place to use it in another, such as reading letters or numbers on one page and then entering them on another page; if you do, they'll probably forget the information and get frustrated.
People can hold 3–4 things in working memory as long as they aren't distracted and their processing of the information is not interfered with.
Chunk or group information into three or four groups if you can't limit the number of topics, or choices to three or four. For example, when you are asking people to choose what to do next, instead of showing them a list of 10 items to click on, group similar items together and show groups with 3–4 items in each group.
From short-term to long-term memory
There are basically two ways for people to create a long-term memory: repeat it a lot, or connect it to something they already know.
If you want people to remember something, then you have to go over it again and again. Practice really does make perfect.
If people can connect new information to information that is already stored, then it's easier to make it stick, or stay in long-term memory, and easier to retrieve it. The existing information is called a schema.
Recognizing is easier than recalling
Recognition makes use of context. And context can help you remember.
Eliminate memory load whenever possible. Make use of UI features such as auto-fill and dropdown lists to reduce the need for people to recall items from memory.
How likely are people to remember a piece of information
You can store concrete words (table, chair) in long-term memory more easily than abstract words (justice, democracy). When possible, use concrete terms and icons. They will be easier to remember than abstract ideas or images.
Information in the middle of a presentation is the least likely to be remembered.
You're most likely to remember what was seen and heard at the end of the talk. This is called the recency effect. If your phone vibrates during a presentation and you stop listening for a minute to text someone, then you are most likely to remember the beginning of the presentation and forget the ending. This is called the suffix effect.
Memories degrade quickly over time
People reconstruct memories each time they remember them.
Memories degrade quickly over time, even the "strongest"ones. Because dramatic memories are so vivid, it was thought that perhaps they were not as subject to forgetting as other memories. But it turns out they are.
Because we know that long-term memory might be faulty, watch out for bias effects when you are conducting user research. It's better to observe what users do rather than ask them what they did in the past.
When information is really important, don't rely on people to remember it. Provide it for them in your design or have a way for them to easily look it up. For example, use dropdown list boxes to show choices rather than assuming users will remember what to fill in.
How people think
Use more clicks and less thinking
If you have to make a trade-off on clicks versus thinking, use more clicks and less thinking. Show people what they need when they need it. Build in links for them to get more information (= progressive disclosure).
Progressive disclosure works only if you know what most people will be looking for at each part of the path—so research is needed.
Cognitive > Visual > Motor loads (effort-wise)
You use up more resources by asking people to think or remember or do a mental calculation (cognitive) than when you ask them to look at something on a screen (visual). You use up more resources when you ask them to look at something or find something on a screen (visual) than when you ask them to press a button or move a mouse (motor). So from a human factors point of view, the order of the loads from most “expensive” to least is: cognitive > visual > motor load.
If you have to add a few clicks but it means the person doesn't have to think or remember as much, that's worth it, because adding clicks is less of a load than thinking. Are there any other trade-offs you can make to reduce mental efforts?
People are prone to mind wandering 30 percent of the time
People will focus on a task for only a limited time. Assume that their minds are wandering often, especially when critical information is at stake.
Make sure you build in feedback about where people are so that if they wander, it's easier for them to get back to the original location or go to the next.
The more uncertain people are, the more defensive they will be
When designing a landing page, you don't know for sure at what phase of the user journey the visitors will be. The more uncertain and not-ready to buy they will be, the more they will argue and be skeptikal of your offer.
The best tactic to use, therefore, might be to ask for a small commitment rather than a large one. This is why free trials work so well. It's a small commitment to sign up for a seven-day free trial and will therefore make it less likely for someone to have a strong reaction and dig in their heels against your product or service.